Radio frequency identification (RFID) systems offer the possibility of inexpensive and efficient management of goods, with applications in inventory control and retail checkout, for example. Each item in an inventory of items, for example in a retail store or a warehouse, may be equipped with an RFID tag, that is, a tag containing an RFID device. The RFID device emits a signal that supplies information about the product to an RFID reader. The information may include product identification, such as manufacturer and item identifiers, such as those provided by a standard universal product code (UPC) bar code. The information may also include a unique serial number, so that each individual item may be easily identified by a reader. Typical RFID readers broadcast a radio frequency (RF) signal. Tags within the range of the reader return a signal to the reader, typically in the form of modulated backscatter of the signal emitted by the reader.
A reader may be placed at a desired inventory control point, such as a retail checkout station or an entrance to or exit of a retail location, warehouse or other area where goods are located. Tags coming within range of the reader are powered by an RF signal emitted by the reader, and transmit tag information which is detected by the reader. The information detected by the reader may be used in operations involving the item or items whose information was detected. Such operations may include entry of a product in a transaction, such as a retail checkout, where items are entered into a transaction record and listed on a receipt. Operations may also include logging the entry or exit of an item from a physical location, for example when items enter or leave a warehouse. The use of RFID in the management of goods offers fast and efficient control of goods.
For example, a customer might bring a cart full of RFID embedded goods to a checkstand, which would sense product identification information for each product, enter each product into a transaction and present the customer with a list of goods in the transaction and a transaction total. A warehouse inventory could be continuously updated by one or more RFID readers located in the warehouse and continually sensing RFID signals from goods located in the warehouse. An RFID reader located at an entry or exit point of a location could record the passage of goods through that location, and could secure the entry or exit point to prevent the unauthorized exit of an item if the item.
The use of RFID devices for management of goods can be expected to allow for a significant reduction in the labor required to enter transactions and to prevent the unauthorized removal of goods. If each item transmits an identifying code that can be detected by a reader, tracking and control of the item may be performed automatically. However, the use of automated equipment to control inventory invites attempts by unscrupulous persons to defeat the automated equipment. One particular vulnerability exhibited by prior art RFID systems is the possibility that a relatively powerful radio frequency (RF) transmitter could overwhelm an RFID reader, rendering it incapable of detecting emissions emanating from an RFID device. A thief who secreted such a device on his or her person or placed it in the vicinity of a reader could hide RFID tagged goods and leave a retail store carrying the goods, without having the goods detected by RFID based checkout or security systems.
There exists, therefore, a need for systems and techniques to prevent the effective disabling of an RFID detector through the use of an RF emitter used to overwhelm the detector and prevent the proper detection of signals transmitted by RFID devices.